"There are countless pundits and other tech gurus describing Google Wave as a disappointment, lately. Most of that seems to come from the fact that nobody seems to get what Wave is for. So they compare it to social media. Is Wave the next Twitter? Nope. Is it the next Facebook? Nope. Is it going to replace Instant Messengers? Possibly, in some circumstances, but not any time soon."Read more here.

Give someone a Wave account, and tell him, that this is his new email.

If this person knows how to use email, he will start by "sending a wave", discovering that he cannot actually "send" it, ask for help, and get the reply that he already sent it.

After that he will just work with it like with email, and discover additional use cases as he goes.
I have no idea, why you think it is too complicated. Quite the reverse, it is easy to begin with, and gets more complex the more advanced features you want to use. But the features are optional, one can get started without knowing the whole lot about it.